Carbon nanotube fibers/filaments formulated from metal nanoparticle catalyst and carbon source

ABSTRACT

Disclosed is a method of: providing a mixture of a polymer or a resin and a transition metal compound, producing a fiber from the mixture, and heating the fiber under conditions effective to form a carbon nanotube-containing carbonaceous fiber. The polymer or resin is an aromatic polymer or a precursor thereof and the mixture is a neat mixture or is combined with a solvent. Also disclosed are a carbonaceous fiber or carbonaceous nanofiber sheet having at least 15 wt. % carbon nanotubes, a fiber or nanofiber sheet having the a polymer or a resin and the transition metal compound, and a fiber or nanofiber sheet having an aromatic polymer and metal nanoparticles.

This application is a divisional application of U.S. Pat. No. 9,926,649,issued on Mar. 27, 2018, which is a divisional application of U.S. Pat.No. 9,255,003, issued on Feb. 9, 2016, which is a continuationapplication of U.S. patent application Ser. No. 13/188,720, filed onJul. 22, 2011, which is a continuation-in-part application of U.S. Pat.No. 8,277,534, issued on Oct. 2, 2012, which claims the benefit of U.S.Provisional Application No. 61/301,279, filed on Feb. 4, 2010. Theseapplications and all other publications and patent documents referred tothroughout this nonprovisional application are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure is generally related to fibers containing carbonnanotubes.

DESCRIPTION OF RELATED ART

High-performance synthetic fibers have been under development for thepast half century, motivated in particular by the high strength andstiffness of the covalent carbon-carbon bond and by the ability toachieve alignment with the fiber axis where they are in the form ofpolymer molecules or graphene sheets. Optimally, one may maximize thenumber of covalently bonded carbon atoms per unit volume or mass (highaverage molecular weight) and thus other types of atoms or groupsattached to polymer chains will tend to reduce ultimate properties. Anadvantage of pure carbon fibers is that the mechanical properties arederived from the in-plane stiffness and strength of graphene sheets,without the adulterating effect of additional atoms to satisfy availablecarbon bonds. However, the route to carbon fibers involves the alignmentof precursor structures, which are then covalently bonded to each otherto create the final structure. Carbon fibers are thus comparativelybrittle, especially when they are heat treated above 1500° C. tomaximize stiffness. The very high axial strength and stiffness ofindividual carbon nanotubes opens up the possibility of processing themdirectly into continuous fibers. Thus, the benefits of high-performancepolymeric fibers, especially directness of processing and fibertoughness, can be combined with the advantages of nanofibers consistingof carbon atoms. The processing routes developed so far to incorporateCNTs into polymeric fibers borrow concepts from polymer fiber processingtechnologies.

Polyacrylonitrile (PAN), petroleum pitch, and cellulosic fibers aretypically used as carbon fiber precursors. Other high temperaturepolymers have also been used. Currently, PAN is the precursor of choice.For converting PAN to carbon and carbon nanotube fibers,thermo-oxidative stabilization typically in the 200-300° C. range is akey step. The PAN fibers are fed through a series of specialized ovensduring the time-consuming oxidative stage. The process combines oxygenmolecules from the air with the PAN fibers in the warp and causes thepolymer chains to start crosslinking. The crosslinked fibers then have adefinite shaped (will not soften) and are then carbonized under inertconditions typically between 700 and ends in a high temperature furnaceat 1200° C. to 1500° C. While dwell times are sometimes proprietary,oxidative dwell time is measured in hours, while carbonization is anorder of magnitude shorter, measured in minutes. As the fiber iscarbonized, it loses weight and volume, contracts by 5 to 10 percent inlength and shrinks in diameter.

There are two main methods for fiber production, namely, liquid andsolid state spinning. Both methods have been developed for CNT-basedfibers. Increased thermal stability, glass transition temperature, andstorage modulus have been reported with the incorporation of carbonnanotubes in various polymer matrices. Poly(p-phenylenebenzobisoxazole)(PBO)/CNT composite fibers containing 10 wt-% CNTsexhibited 50% higher tensile strength compared to the controlled PBOfiber. Polyacrylonitrile (PAN) copolymers are commercially important andare used as carbon fiber precursors as well as for the development ofporous and activated carbon for a variety of applications. Films havebeen made from PAN/MWNT homogeneous dispersions. The CNTs can bedispersed in solvents such as dimethylformamide (DMF) anddimethylacetamide (DMAC). Carbonized and activated PAN/CNT films arevery promising for supercapacitor electrode applications. Solution spunPAN/CNT fibers containing 10 wt-% nanotubes exhibit a 100 percentincrease in tensile modulus at room temperature, a significant reductionin thermal shrinkage, and a 40° C. increase in the glass transitiontemperature. These observations provide evidence of the interactionbetween PAN and the CNTs.

One parameter in making high-strength fibers from carbon nanotubes isthe availability of nanotubes which are as long and as structurallyperfect as possible. Another parameter is to align all nanotubes asperfectly as possible with the fiber axis, so as to maximize thetranslation of their axial properties to those of the fiber. The bondingbetween adjacent nanotubes is weak in shear (graphite is a lubricant)and thus as great a contact length as possible is necessary to transferthe load into any given nanotube. Another advantage of thin wallednanotubes (single or double) is that they tend to facet or flatten so tomaximize their contact area. Alignment is typically achieved throughmechanical forces whether applied to a partly linked array of fibers orthrough fluid-flow forces on a lyotropic suspension.

Today, there is currently an intense effort throughout the scientificcommunity to efficiently disperse MWNTs into polymeric fibers to takeadvantage of the exceptional mechanical properties of carbon nanotubes.Moreover, various research groups have used aerogels and fuming sulfuricacid to utilize the CNTs grown by chemical vapor deposition (CVD) in theformation of CNT containing fibers. Carbon fibers derived frompolyacrylonitrile (PAN) have been the dominant reinforcement in advancedcomposites since their commercialization in the late 1960s. By using aresin such as PAN, which can be spun into a fiber, cured, and thencarbonized, the formation of CNT fibers can be exploited using the NRLbreakthrough method for the formation of CNTs by heating the PAN orother carbon sources in the presence of small metal nanoparticles thatmay be magnetic in nature.

BRIEF SUMMARY

Disclosed herein is a method comprising: providing a mixture of apolymer or a resin and a transition metal compound, producing a fiberfrom the mixture, and heating the fiber under conditions effective toform a carbon nanotube-containing fiber. The polymer or resin is anaromatic polymer or a precursor thereof and the mixture is a neatmixture or is combined with a solvent.

Also disclosed herein is a fiber or nanofiber sheet comprising at least15 wt. % carbon nanotubes.

Also disclosed herein is a fiber or nanofiber sheet comprising a mixtureof: a polymer or a resin, as described above, and a transition metalcompound.

Also disclosed herein is a fiber or nanofiber sheet comprising: anaromatic polymer and metal nanoparticles.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the disclosure will be readily obtainedby reference to the following Description of the Example Embodiments andthe accompanying drawings.

FIG. 1 shows photographs of large CNT-containing fibers and rodsformulated from PAN and phthalonitrile, respectively.

FIGS. 2 and 3 show SEM images showing the crude fibers and the CNTsappearing somewhat aligned within the fibers.

FIG. 4 shows a synthetic scheme for an embodiment of the method.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

In the following description, for purposes of explanation and notlimitation, specific details are set forth in order to provide athorough understanding of the present disclosure. However, it will beapparent to one skilled in the art that the present subject matter maybe practiced in other embodiments that depart from these specificdetails. In other instances, detailed descriptions of well-known methodsand devices are omitted so as to not obscure the present disclosure withunnecessary detail.

A high-yield method has been developed for the production of carbonnanotubes (CNTs) and carbon nanotube-magnetic metal nanoparticlecompositions in a bulk carbonaceous solid. The yield of CNT formationcan be controlled as a function of the carbonization temperature andexposure time at elevated temperatures. With this method, CNTs areformed in a bulk carbonaceous solid from thermal decomposition ofvarious amounts of an organometallic compound and/or metal salts in thepresence of an excess amount of a carbon source such as selected highlyaromatic compounds. Only a small amount of the organometallic compoundor metal salt is needed to achieve the formation of CNTs in high yield,but larger quantities of the metal source can also be incorporated, ifdesired.

The disclosed process is concerned with the formation of neat alignedCNT fibers from precursor compositions formulated from (1) a carbonsource such as polyacrylonitrile (PAN) or copolymers thereof,pitch-based compounds, high temperature compounds or resins that charand (2) a metal salt(s) and/or organometallic compound(s). The spinningof fibers occurs from the precursor compositions either melted ordissolved or dispersed in a dipolar aprotic solvent, and thermaltreatment of the precursor composition resulting in the decomposition ofthe metal salt and/or organometallic compounds into metal nanoparticlesthat behave as the catalyst for the formation of the CNTs. Heattreatment at, for example, 200-400° C. is important to convert thepolymeric fibers to a form with retention of structural integrity forheating to elevated temperatures and for conversion of the fibers above,for example, 500° C. to metal nanoparticle/carbon nanotube fibers duringa carbonization process. The carbonization process to form the carbonnanotube fibers occurs in temperature steps from, for example, about600° C. to 1500° C. The property of the carbon nanotube fibers willdepend on the heat treatment.

The process may result in the high-yield formation of multi-walledcarbon nanotubes (MWNTs) in the solid carbonaceous domain upon heattreatment to elevated temperatures under ambient pressure. The methodpermits the large-scale inexpensive production of MWNTs in a shaped,solid configuration. The MWNTs are formed under atmospheric pressureduring the carbonization process above 500° C. in the carbonaceoussolid. The catalytic metal atoms, nanoclusters, and/or nanoparticlesformed from the decomposition of the organometallic compound or metalsalt are the key to the formation of the carbon nanotubes in thedeveloping carbonaceous nanomaterial by reacting with the developingpolycondensed aromatic ring system. To date, the average size asdetermined by X-ray diffraction studies are 5-30 nm. Small metalnanoparticles (1-3 nm) could produce single-walled carbon nanotubes. Thecomposition can be tailored to have mainly CNTs or varying amounts ofCNTs and magnetic metal nanoparticles, as formed. Shaped solid forms,films, and fibers/rods can be readily formulated from the precursormixtures. If desired, CNT-containing powders can be obtained by millingof the carbonaceous solid. The CNT content of the bulk solid can becontrolled by the final pyrolysis temperature. For example, a finalpyrolysis temperature of 800° C. and 1300° C. may afford a CNT contentof approximately 20 and 70 wt. %, respectively. A suitable range ofpyrolysis temperatures includes, but is not limited to, 600-2700° C.

The initial fiber form of the initial materials may be made by a varietyof methods that are known in the art including, but not limited to,spinning with a spinneret, electrospinning, solvent precipitation, andphysically pulling a fiber from a mixture of the materials. A variety ofsuch methods are described in U.S. Provisional Application No.61/301,279. The materials may be mixed neat in the melt or liquid state,or mixed or dissolved in a solvent. When the precursor composition iscompletely dissolved in a solvent, it can help to ensure that metalsalt(s) and/organometallic compounds are deposited within the spunpolymeric fibers. The fiber is a threadlike material and may have thesame dimensions as is typical for other carbon fibers.

The polymer or resin may be dissolved in a solution simultaneously,before, or after dissolving the transition metal compound. Thetransition metal compound may be dissolved close in time to theproduction of the fiber from the same solution. This may be done toavoid decomposition of certain transition metal compounds, such asCo₂(CO)₈. Such decomposition may occur gradually over time, particularlyif exposed to air or elevated temperatures. The fibers may be producedwhen at least 50%, 70%, or 90% of the original amount of the transitionmetal compound still remains in the solution without having decomposed.For example, the solution may be spun into fibers within 30 days ofdissolving the transition metal compound in the solution. A polaraprotic solvent may be used for dissolving both components. Suchsolvents are known in the art and include, but are not limited to,dimethylacetamide, dimethylformamide, dimethyl sulfoxide, andN-methylpyrrolidone. Any concentration of transition metal compound thatresults in the formation of carbon nanotubes may be used, includingconcentrations higher and lower than used in the examples below.

Suitable carbon sources include aromatic polymers and precursorsthereof. The polymer may be a crosslinked or thermoset polymer, with thecrosslinking occuring during or after formation of the fiber. Thearomatic polymer may be an aromatic phthalonitrile polymer or oligomer,or a thermoset thereof, such as a phthalonitrile oligomer made frombisphenol A and benzophenone. A precursor is a compound or material thatcan be converted to an aromatic polymer or material by heating beforeforming the CNTs. Such heating may be in oxygen, including atmosphericair. The heating may be, for example, from 200-300° C. When heated inthis way, PAN converts to an aromatic polymer as the side groups formrings. Pitch resins such as coal pitch (coal tar pitch), petroleumpitch, or synthetic pitches also form aromatic materials. Other suitablecarbon sources include any aromatic material, or material that convertsto an aromatic, that forms a char when heated in an inert atmosphere.Such materials and their products are disclosed in U.S. Pat. Nos.6,673,953; 6,770,583; 6,846,345; 6,884,861; and 7,819,938.

The transition metal compound may be, for example, a metal salt or anorganometallic compound. Such compounds can decompose at elevatedtemperatures to form metal nanoparticles. Such suitable compoundsinclude, but are not limited to, octacarbonyldicobalt,1-(ferrocenylethynyl)-3-(phenylethynyl)benzene, diironnonacarbonyl, andbis(1,5-cyclooctodiene)nickel(0).

The small metal nanoparticles, formed by thermaldegradation/decomposition of the metal salt(s) and/or organometalliccompounds, are responsible for the formation of the CNTs within thecarbonized fiber upon heat treatment to elevated temperatures. Theprecursor polymeric fibers (carbon source and metal salt) may becarbonized by the simple carbonization process already used to producecarbon and graphitic fibers.

The precursor compositions such as polyacrylonitrile, phthalonitriles,petroleum pitches, etc. and metal salts and/or organometallic compoundare mixed and heated to cause the decomposition of the metal componentinto metal atoms, clusters, and/or metal nanoparticles (controlling themetal particle size to less than 25 nm). The small metal nanoparticlesare responsible for and catalyze the formation of the CNTs. Large metalnanoparticles larger than 40 nm in size may afford graphite; thus it maybe important to keep the metal catalyst at much smaller sizes.Stretching may help to align the molecules within the small diametersized fibers and provides the basis for the formation of the tightlybonded carbon crystals after carbonization and the means for aligningthe CNTs within the fibers.

Carbon nanotube fibers may be fabricated by injecting a solution of aprecursor composition formulated from a carbon source-metal saltand/organometallic compound into a protic solvent such as water, bydrawing from the melt of a B-staged thermoset resin at elevatedtemperatures or by conventional spinning techniques of a carbonprecursor followed by carbonization of the polymeric fibers formed bythe listed methods of preparation. In an effort to develop a method forthe fabrication of CNT fibers formulated directly from the precursorcarbon material, experiments have been conducted whereby fibers weredrawn from the melt of a Fe₂(CO)₉/phthalonitrile precursor compositionand by the deposition of a fiber into water from a solution ofFe₂(CO)₉/polyacrylonitrile (PAN) and a dipolar aprotic solvent. Thepolymeric fibers were used in the direct formation of the carbonnanotube (MWNT) fibers by slowly heating to 1000° C. under inertconditions. Studies show that any CNT precursor composition formulationfrom a carbon source and a metal salt(s) and/or organometallic compoundthat can be spun or drawn into a fiber and carbonized by the method canbe converted into carbon nanotube fibers. There are no known priorreports of the ability to achieve the direct formation of CNT fibersusing a simple carbonization process from precursor materials such asPAN and petroleum pitches that are currently used to form carbon andgraphitic fibers. To show the feasibility of forming CNT fibers, largediameter fibers and rods were formed from a phthalonitrile oligomer andPAN and converted into CNT large fibers and rods (see FIG. 1).

Since the formation of CNTs can occur directly from a mixture of a metalsalt such as Fe₂(CO)₉, Co₂(CO)₈, and nickel(cyclooctadiene) and carbonsources such as PAN or phthalonitriles in a shaped composition includinglarge diameter fibers and rods, these precursor compositions aresuitable candidates to spin polymeric fibers that can be directlyconverted into MWNT-fibers during the carbonization process. The fibersmay also contain various quantities of magnetic metal

nanoparticles depending upon the initial concentration of the metalsalt(s) or organometallic compound(s) in the precursor composition. Thephotographs (see FIG. 1) show carbon nanotube fibers obtained from PAN(top) and phthalonitrile (bottom). Upon cure and carbonization of thepolymeric fibers, x-ray diffraction (XRD) and transmission electronmicroscopy (TEM) studies confirmed the presence of copious amounts ofMWNTs in the carbonized fibers. Scanning electron microscopy (SEM)images (see FIGS. 2 and 3) show that the CNTs can be potentially alignedwithin small diameter sized fibers (micron-and nanometer-sized fibers).No stretching of the fibers/rod was performed during these experiments.

The formation and heat treatment of the fibers may be similar to methodknown in the art for that of the same materials in the absence of thetransition metal compound. A variety of such methods are described inU.S. Provisional Application No. 61/301,279.

The resulting fiber may have at least 5, 10, 15, 20, 25, 30, 35, 40, 45,50, 55, 60, 65, 70, 75, or 80 wt. % CNTs. The CNTs may be generallyaligned parallel with each other and the length of the fiber. The fibermay also contain metal nanoparticles. However, if heated to a highenough temperature the metal nanoparticles may be removed. Theseproperties also apply to nanofiber sheets.

Many potential applications have been proposed for carbon nanotubes,including conductive and high-strength composites; energy storage andenergy conversion devices; sensors; field emission displays andradiation sources; hydrogen storage media; and nanometer-sizedsemiconductor devices, probes, high electrical current flow, andinterconnects. Some of these applications are now realized in products.Another potential application is use is in garments, such asanti-ballistic and decontamination garments. The small diameter sized,high surface area CNT fibers would be expected to exhibit superiormechanical, electrical, magnetic, catalytic, and optical properties.Potential payoffs and impact areas of the CNT fibers include structural,motor/generator, energy (fuel cell electrodes, Li-batteries, hydrogenstorage, and electricity carrier—electrically conductive carbonnanotubes), membrane for water purification, air filtration (toxinremoval), and various catalytic applications. Metal nanoparticles alsopresent in the fibers could be of importance for many of theseapplications.

The following examples are given to illustrate specific applications.These specific examples are not intended to limit the scope of thedisclosure in this application.

EXAMPLE 1

Synthesis of 1/20 by weight octacarbonyldicobalt/polyacrylonitrilemixture—Co₂(CO)₈(50 mg, 0.146 mmol), polyacrylonitrile (“PAN”) (1.00 g)and 10 mL of methylene chloride were added to a 50 mL round bottomedflask. The Co₂(CO)₈ readily dissolved in the methylene chloride. The PANdid not dissolve. The slurry was allowed to stir for 5 min before thesolvent was removed under reduced pressure. The mixture was vacuum driedand isolated as an off-white solid.

EXAMPLE 2

Thermal conversion of 1/20 by weight Co₂(CO)₈/PAN mixture to carbonnanotube-cobalt nanoparticle composition by heating to 1000° C.—A sampleof the mixture from Example 1 (22.8 mg) was heated in a TGA chamberunder nitrogen at 10° C./min to 1000° C. resulting in a shapedcomposition and a char yield of 36%. The DTA curve showed an exotherm at308° C. X-ray studies confirmed the presence of carbon nanotubes-cobaltnanoparticles in the carbon composition. The x-ray diffraction studyshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for fcc-cobaltnanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 3

Thermal conversion of 1/20 by weight Co₂(CO)₈/PAN mixture to carbonnanotube-cobalt nanoparticle composition by heating to 1500° C.—A sampleof the mixture from Example 1 (21.5 mg) was heated in a TGA chamberunder nitrogen at 10° C./min to 1500° C. resulting in a shapedcomposition and a char yield of 32%. The DTA curve showed an exotherm at310° C. X-ray studies confirmed the presence of carbon nanotubes-cobaltnanoparticles in the carbon composition. The x-ray diffraction studyshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for fcc-cobaltnanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 4

Pre-oxidation and thermal conversion of 1/20 by weight Co₂(CO)₈/PANmixture to carbon nanotube-cobalt nanoparticle composition—A sample ofthe mixture prepared as in Example 1 (25.52 mg) was heated in a TGAchamber at 10° C./min to 280° C. under air and isothermed for 1.5 hr.The resulting air stabilized solid was further heated at 10° C./min to1000° C. under nitrogen resulting in a shaped composition and an overallchar yield of 45%. X-ray studies confirmed the presence of carbonnanotubes-cobalt nanoparticles in the carbon composition. The x-raydiffraction study showed the four characteristic reflection values[(002), (100), (004), and (110)] for carbon nanotubes and the patternfor fcc-cobalt nanoparticles. The x-ray (002) reflection for carbonnanotubes was readily apparent.

EXAMPLE 5

Synthesis of 1/40 by weight Co₂(CO)₈/PAN mixture—Co₂(CO)₈ (20 mg, 0.0584mmol), PAN (1.00 g) and 10 mL of methylene chloride were added to a 50mL round bottomed flask. The Co₂(CO)₈ readily dissolved in the methylenechloride. The PAN did not dissolve. The slurry was allowed to stir for 5min before the solvent was removed under reduced pressure. The mixturewas vacuum dried and isolated as an off-white solid.

EXAMPLE 6

Thermal conversion of 1/40 by weight Co₂(CO)₈/PAN mixture to carbonnanotube-cobalt nanoparticle composition by heating to 1000° C. and1400° C.—Sample of the mixture from Example 5 (25.04 mg and 30.26 mg)were heated in a TGA chamber under nitrogen at 10° C./min to 1000° C.and 1400° C. resulting in a shaped composition and char yields of 37%and 34%, respectively. The DTA curve showed an exotherm at 304° C. X-raystudies confirmed the presence of carbon nanotubes-cobalt nanoparticlesin the carbon composition. The x-ray diffraction studies showed the fourcharacteristic reflection values [(002), (100), (004), and (110)] forcarbon nanotubes and the pattern for fcc-cobalt nanoparticles. The x-ray(002) reflection for carbon nanotubes was readily apparent.

EXAMPLE 7

Pre-oxidation and thermal conversion of 1/40 by weight Co₂(CO)₈/PANmixture to carbon nanotube-cobalt nanoparticle composition—A sample ofthe mixture prepared as in Example 5 (26.75 mg) was heated in a TGAchamber at 10° C./min to 280° C. under air and isothermed for 1.5 hr.The resulting air stabilized solid was further heated at 10° C./min to1000° C. under nitrogen resulting in a shaped composition and an overallchar yield of 47%. X-ray studies confirmed the presence of carbonnanotubes-cobalt nanoparticles in the carbon composition. The x-raydiffraction study showed the four characteristic reflection values[(002), (100), (004), and (110)] for carbon nanotubes and the patternfor fcc-cobalt nanoparticles. The x-ray (002) reflection for carbonnanotubes was readily apparent.

EXAMPLE 8

Synthesis of 1/100 by weight Co₂(CO)₈/PAN mixture—Co₂(CO)₈ (10 mg,0.0292 mmol), PAN (1.00 g) and 10 mL of methylene chloride were added toa 50 mL round bottomed flask. The Co₂(CO)₈ readily dissolved in themethylene chloride. The PAN did not dissolve. The slurry was allowed tostir for 5 min before the solvent was removed under reduced pressure.The mixture was vacuum dried and isolated as an off-white solid.

EXAMPLE 9

Thermal conversion of 1/100 by weight Co₂(CO)₈/PAN mixture to carbonnanotube-cobalt nanoparticle composition by heating to 1000° C.—A sampleof the mixture from Example 8 (25.32 mg) was heated in a TGA chamberunder nitrogen at 10° C./min to 1000° C. resulting in a shapedcomposition and a char yield of 35%. The DTA curve showed an exotherm at295° C. X-ray studies confirmed the presence of carbon nanotubes-cobaltnanoparticles in the carbon composition. The x-ray diffraction studiesshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern (small intensity) forfcc-cobalt nanoparticles. The x-ray (002) reflection for carbonnanotubes was readily apparent.

EXAMPLE 10

Synthesis of 1/20 by weight1-(ferrocenylethynyl)-3-(phenylethynyl)benzene/PANmixture—1-(Ferrocenylethynyl)-3-(phenylethynyl) benzene (10 mg, 0.0259mmol), PAN (500 mg) and 10 mL of methylene chloride were added to a 50mL round bottomed flask. The 1-(ferrocenylethynyl)-3-(phenylethynyl)benzene readily dissolved in the methylene chloride. The PAN did notdissolve. The slurry was allowed to stir for 10 min before the solventwas removed under reduced pressure. The mixture was vacuum dried andisolated as an orange solid.

EXAMPLE 11

Thermal conversion of 1/20 by weight1-(ferrocenylethynyl)-3-(phenylethynyl)-benzene/PAN mixture to carbonnanotube-iron nanoparticle composition by heating to 1000° C. and 1500°C.—Samples of the mixture from Example 10 (30.26 mg and 32.56 mg) wereheated in a TGA chamber under nitrogen at 10° C./min to 1000° C. and to1500° C. resulting in a shaped composition and char yields of 33% and30%, respectively. The DTA curves showed an exotherm at 297° C. X-raystudies confirmed the presence of carbon nanotubes-iron nanoparticles inthe carbon compositions. The x-ray diffraction studies showed the fourcharacteristic reflection values [(002), (100), (004), and (110)] forcarbon nanotubes and the pattern for bcc-iron nanoparticles. The x-ray(002) reflection for carbon nanotubes was readily apparent.

EXAMPLE 12

Pre-oxidation and thermal conversion of 1/20 by weight1-(ferrocenylethynyl)-3-(phenylethynyl)-benzene/PAN mixture to carbonnanotube-iron nanoparticle composition by heating to 1000° C. and 1500°C.—Samples of the mixture from Example 10 (35.46 mg and 38.87 mg) wereheated in a TGA chamber at 10° C./min to 280° C. under air andisothermed for 3.5 hr. The air stabilized samples were then heated undernitrogen at 10° C./min to 1000° C. and to 1500° C. resulting in a shapedcomposition and char yields of 48% and 45%, respectively. X-ray studiesconfirmed the presence of carbon nanotubes-iron nanoparticles in thecarbon compositions. The x-ray diffraction studies showed the fourcharacteristic reflection values [(002), (100), (004), and (110)] forcarbon nanotubes and the pattern for bcc-iron nanoparticles. The x-ray(002) reflection for carbon nanotubes was readily apparent.

EXAMPLE 13

Synthesis of 1/20 by weight diironnonacarbonyl/PAN mixture—Fe₂(CO)₉ (250mg, 0.688 mmol), PAN (5.00 g) and 10 mL of methylene chloride or acetonewere added to a 50 mL round bottomed flask. The Fe₂(CO)₉ readilydissolved in the methylene chloride or acetone. The PAN did notdissolve. The slurry was allowed to stir for 15 min before the solventwas removed under reduced pressure. The mixture was vacuum dried andisolated as an orange solid.

EXAMPLE 14

Thermal conversion of 1/20 by weight Fe₂(CO)₉/PAN mixture to carbonnanotube-iron nanoparticle composition by heating to 1000° C.—A sampleof the mixture from Example 13 (25.11 mg) was heated in a TGA chamberunder nitrogen at 10° C./min to 1000° C. resulting in a shapedcomposition and a char yield of 36%. The DTA curve showed an exotherm at308° C. X-ray studies confirmed the presence of carbon nanotubes-ironnanoparticles in the carbon composition. The x-ray diffraction studiesshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for bcc-ironnanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 15

Thermal conversion of 1/20 by weight Fe₂(CO)₉/PAN mixture to carbonnanotube-iron nanoparticle composition by heating to 1500° C.—A sampleof the mixture from Example 13 (21.8 mg) was heated in a TGA chamberunder nitrogen at 10° C./min to 1500° C. resulting in a shapedcomposition and a char yield of 32%. The DTA curve showed an exotherm at310° C. X-ray studies confirmed the presence of carbon nanotubes-ironnanoparticles in the carbon composition. The x-ray diffraction studiesshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for bcc-ironnanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 16

Pre-oxidation and thermal conversion of 1/20 by weight Fe₂(CO)₉/PANmixture to carbon nanotube-iron nanoparticle composition—A sample of themixture from Example 13 (50 mg) was heated in a TGA chamber at 10°C./min to 280° C. under air and isothermed for 2 hr. The resulting solidwas further heated at 10° C./min to 1000° C. under nitrogen resulting ina shaped composition and an overall char yield of 40%. X-ray studiesconfirm the presence of carbon nanotubes-iron nanoparticles in thecarbon composition. The x-ray diffraction studies showed the fourcharacteristic reflection values [(002), (100), (004), and (110)] forcarbon nanotubes and the pattern for bcc-iron nanoparticles. The x-ray(002) reflection for carbon nanotubes was readily apparent.

EXAMPLE 17

Synthesis of 1/20 by weight Fe₂(CO)₉/PAN mixture by adding Fe₂(CO)₉dropwise—Fe₂(CO)₉ (750 mg, 2.06 mmol) in 10 mL of methylene chloride wasadded dropwise to a mixture of PAN (15.00 g) and 20 mL of methylenechloride in a 50 mL round bottomed flask. The Fe₂(CO)₉ readily dissolvedin the methylene chloride. The PAN did not dissolve. The slurry wasallowed to stir for 5 min before the solvent was removed under reducedpressure. The mixture was vacuum dried and isolated as an orange solid.

EXAMPLE 18

Thermal conversion of 1/20 by weight Fe₂(CO)₉/PAN mixture (dropwiseaddition of Fe₂(CO)₉) to carbon nanotube-iron nanoparticle compositionby heating to 1500° C.—A sample of the mixture from Example 17 (75.6 mg)was heated in a TGA chamber under nitrogen at 10° C./min to 1500° C.resulting in a shaped composition and a char yield of 37%. The DTA curveshowed an exotherm at 310° C. X-ray studies confirmed the presence ofcarbon nanotubes-iron nanoparticles in the carbon composition. The x-raydiffraction studies showed the four characteristic reflection values[(002), (100), (004), and (110)] for carbon nanotubes and the patternfor bcc-iron nanoparticles. The x-ray (002) reflection for carbonnanotubes was readily apparent.

EXAMPLE 19

Synthesis of 1/20 molar Co₂(CO)₈/phthalonitrile mixture—Thephthalonitrile resin (a 2:1 oligomer of bisphenol A and benzophenonecapped with phthalonitrile units, hereinafter “phthalonitrile”) (200 mg,0.225 mmol) was dissolved in 10 mL of methylene chloride in a 25 mLround bottomed flask. Co₂(CO)₈ (10 mg, 0.0292 mmol) dissolved in 2 mL ofhexanes was added and a brown precipitate formed. The solvent wasremoved under reduced pressure, the mixture vacuum was dried, and theproduct was isolated as a dark brown solid.

EXAMPLE 20

Thermal conversion of 1/20 molar Co₂(CO)₈/phthalonitrile mixture tocarbon nanotube-cobalt nanoparticle composition by heating to 1000° C.and to 1500° C.—Samples of the mixture from Example 19 (38.01 mg and33.75 mg) were heated in a TGA chamber under nitrogen at 10° C./min to1000° C. resulting in a shaped composition and a char yield of 47%. TheDTA curve showed exotherms at 163, 276, 514, and 868° C. X-ray studiesconfirmed the presence of carbon nanotubes-cobalt nanoparticles in thecarbon composition. The x-ray diffraction studies showed the fourcharacteristic reflection values [(002), (100), (004), and (110)] forcarbon nanotubes and the pattern for fcc-cobalt nanoparticles. The x-ray(002) reflection for carbon nanotubes was readily apparent.

EXAMPLE 21

Direct formation of fibers from melt of 1/20 molarCo₂(CO)₈/phthalonitrile mixture to carbon nanotube-cobalt nanoparticlecomposition and heating of stabilized fiber to 1000° C.—A sample (0.25g) of the mixture from Example 19 was melted on a hot plate and heatedat 330° C. to a viscous melt followed by the insertion of a glass rodinto the sample and the upward drawing of fibers. The diameter of thefibers was controlled as a function of the rate of drawing of thefibers. The drawn fibers were cured or solidified by heating at 280° C.for 12 hr, 300° C. for 2 hr, 350° C. for 3 hr, and 375° C. to form athermoset fiber, which was carbonized by heating at 2° C./min in a flowof nitrogen. Drawing the fibers at 325° C. permitted the retention ofshape during the curing process. The x-ray diffraction and transmissionelectron microscopy (TEM) studies showed the presence of carbonnanotubes within the fibers.

EXAMPLE 22

Thermal conversion of 1/20 molarCo₂(CO)₈/phthalonitrile/bis[4-(3-aminophenoxy)phenyl]sulfone mixture tocarbon nanotube-cobalt nanoparticle composition by heating to 1000° C.—Asamples of the mixture prepared as in Example 19 (100 mg) was mixed andmelted with bis[4-(3-aminophenoxy)phenyl]sulfone (p-BAPS) (2 mg) at 180°C. The resulting mixture was cooled and a sample (61.75 mg) was curedunder nitrogen in a TGA chamber by heating at 250° C. for 1 hr, 300° C.for 2 hr, 350° C. for 6 hr, and 375° C. for 4 hr. The shaped compositionwas cooled and a sample (84.65 mg) was heated under nitrogen at 10°C./min to 1000° C. resulting in a char yield of 67%. The DTA curveshowed exotherms at 530 and 751° C. X-ray studies confirmed the presenceof carbon nanotubes-cobalt nanoparticles in the carbon composition. Thex-ray diffraction studies showed the four characteristic reflectionvalues [(002), (100), (004), and (110)] for carbon nanotubes and thepattern for fcc-cobalt nanoparticles. The x-ray (002) reflection forcarbon nanotubes was readily apparent.

EXAMPLE 23

Thermal conversion of 1/20 molar Co₂(CO)₈/phthalonitrile/p-BAPS mixtureto carbon nanotube-cobalt nanoparticle composition by heating to 1500°C.—A samples of the mixture prepared as in Example 19 (150 mg) was mixedand melted with p-BAPS (3 mg) at 180° C. The resulting mixture wascooled and a sample (75.23 mg) was cured under nitrogen in a TGA chamberby heating at 250° C. for 1 hr, 300° C. for 2 hr, 350° C. for 6 hr, and375° C. for 4 hr. The shaped composition was cooled and a sample (65.24mg) was heated under nitrogen at 10° C./min to 1000° C. resulting in achar yield of 67%. The DTA curve showed exotherms at 530 and 751° C.X-ray studies confirmed the presence of carbon nanotubes-cobaltnanoparticles in the carbon composition. The x-ray diffraction studiesshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for fcc-cobaltnanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 24

Thermal conversion of 1/20 molar Co₂(CO)₈/phthalonitrile/p-BAPS mixtureto carbon nanotube-cobalt nanoparticle fibers by heating to 1500° C.—Asamples of the mixture prepared as in Example 19 (500 mg) was mixed andmelted with p-BAPS (10 mg) at 180° C. The resulting sample was placed ona hot plate and heated at 330° C. to a viscous melt followed by theinsertion of a glass rod into the sample and the upward drawing offibers. The diameter of the fibers was controlled as a function of therate of drawing of the fibers. The drawn fibers were cured or solidifiedby heating at 280° C. for 12 hr, 300° C. for 2 hr, 350° C. for 3 hr, and375° C. for 4 hr to form a thermoset fiber, which was carbonized byheating at 2° C./min in a flow of nitrogen. Drawing the fibers at 325°C. permitted the retention of shape during the curing process, which wasinitiated at a lower temperature (270° C.) so that the fiber wouldretain its solid shape while curing to a thermoset fiber. The x-raydiffraction and transmission electron microscopy (TEM) studies showedthe presence of carbon nanotubes within the fibers. X-ray studiesconfirmed the presence of carbon nanotubes-cobalt nanoparticles in thecarbonized fibers/rods. The x-ray diffraction studies showed the fourcharacteristic reflection values [(002), (100), (004), and (110)] forcarbon nanotubes and the pattern for fcc-cobalt nanoparticles. The x-ray(002) reflection for carbon nanotubes was readily apparent.

EXAMPLE 25

Synthesis of 1/20 molar Fe₂(CO)₉/phthalonitrile mixture—Thephthalonitrile (200 mg, 0.225 mmol) was dissolved in 10 mL of methylenechloride in a 25 mL round bottomed flask. Fe₂(CO)₉ (8.2 mg, 0.0225 mmol)dissolved in 2 mL of hexanes was slowly added and a brown precipitateformed. The solvent was removed under reduced pressure, the mixturevacuum was dried, and the Fe₂(CO)₉/phthalonitrile mixture was isolatedas a solid.

EXAMPLE 26

Thermal conversion of 1/20 molar Fe₂(CO)₉/phthalonitrile mixture tocarbon nanotube-cobalt nanoparticle composition by heating to 1000° C.and 1500° C.—Samples of the mixture from Example 25 (38.01 mg and 50.26mg) were heated in a TGA chamber under nitrogen at 10° C./min to 1000°C. and to 1500° C. resulting in a shaped composition and char yields of47% and 43%, respectively. The DTA curve showed exotherms at 163, 276,514, and 868° C. during the heat treatment to 1000° C. and to 1500° C.X-ray studies confirmed the presence of carbon nanotubes-ironnanoparticles in the carbon composition. The x-ray diffraction studiesshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for fcc-Conanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 27

Synthesis of 1/20 molar bis(1,5-cyclooctodiene)nickel (0)/phthalonitrilemixture—The phthalonitrile (1.00 g, 1.12 mmol) was dissolved in 25 mL ofmethylene chloride in a 50 mL round bottomed flask. Ni[COD]₂ (27.5 mg,0.100 mmol) dissolved in 2 mL of methylene chloride was added dropwiseand a brown precipitate formed. The solvent was removed under reducedpressure, the mixture vacuum was dried, and the mixture was isolated asa dark brown solid.

EXAMPLE 28

Thermal conversion of 1/20 molar Ni[COD]₂/phthalonitrile mixture tocarbon nanotube-nickel nanoparticle composition by heating to 1000° C.—Asample of the mixture from Example 27 (46.2 mg) was heated in a TGAchamber under nitrogen at 10° C./min to 1000° C. resulting in a shapedcomposition and a char yield of 50%. X-ray studies confirm the presenceof carbon nanotubes-nickel nanoparticles in the carbon composition. Thex-ray diffraction studies showed the four characteristic reflectionvalues [(002), (100), (004), and (110)] for carbon nanotubes and thepattern for nickel nanoparticles. The x-ray (002) reflection for carbonnanotubes was readily apparent.

EXAMPLE 29

Synthesis of 1/20 by weight Co₂(CO)₈/coal pitch mixture—A coal tar pitch(1.18 g) and Co₂(CO)₈ (59 mg, 0.172 mmol) were mixed together in 5 mL ofmethylene chloride. The mixture was stirred for 5 min and the solventwas removed under reduced pressure. The mixture was vacuum dried and theproduct isolated as a black oil.

EXAMPLE 30

Heating of 1/20 by weight Co₂(CO)₈/coal pitch mixture to 1100° C. and1400° C.—Samples of the mixture from Example 29 (45.92 mg and 35.43 mg)were heated at 10° C./min to 1100° C. and to 1400° C. in a TGA chamberunder nitrogen resulting in shaped components to afford char yields of30% and 27%, respectively. X-ray studies confirmed the presence ofcarbon nanotubes-cobalt nanoparticles in the carbon compositions. Thex-ray diffraction studies showed the four characteristic reflectionvalues [(002), (100), (004), and (110)] for carbon nanotubes and thepattern for fcc-cobalt and cobalt oxide nanoparticles. The x-ray (002)reflection for carbon nanotubes was readily apparent.

EXAMPLE 31

Synthesis of 1/20 by weight Co₂(CO)₈/petroleum pitch mixture—Thepetroleum pitch (1.05 g) and Co₂(CO)₈ (53 mg, 0.154 mmol) were mixedtogether in 5 mL of methylene chloride. The mixture was stirred for 5min and the solvent was removed under reduced pressure. The mixture wasvacuum dried and the product was isolated as a black oil.

EXAMPLE 32

Heating of 1/20 by weight Co₂(CO)₈/petroleum pitch mixture to 1000° C.and 1500° C.—Samples of the mixture from Example 31 (52.22 mg and 55.66mg) were heated at 10° C./min to 1000° C. and to 1500° C. under nitrogenresulting in a shaped component to afford char yields of 29% and 26%,respectively. X-ray studies confirmed the presence of carbonnanotubes-cobalt nanoparticles in the carbon composition. The x-raydiffraction studies showed the four characteristic reflection values[(002), (100), (004), and (110)] for carbon nanotubes and the patternfor fcc-cobalt and cobalt oxide nanoparticles. The x-ray (002)reflection for carbon nanotubes was readily apparent.

EXAMPLE 33

Synthesis of 1/20 by weight Co₂(CO)₈/naphthalene-derived mesophase pitch(AR pitch resin by Mitsubishi) mixture—The AR pitch resin (1.05 g) andCo₂(CO)₈ (53 mg, 0.154 mmol) were mixed together in powdered form andheated to 270° C. with stirring by mechanical means under inertcondition. The sample was then cooled to room temperature.

EXAMPLE 34

Conversion of 1/20 by weight Co₂(CO)₈/naphthalene-derived mesophasepitch (AR pitch resin by Mitsubishi) mixture to carbon nanotubes—ASample (50 mg) of the mixture from Example 33 was oxidatively stabilizedin a flow (50 cc/min) of air at 290° C. for 1 hr, cooled and then heatedat 10° C./min to 1500° C. under nitrogen. The air stabilizationconverted the melt to a solid so that the resulting composition retainedits structure upon further heating to elevated temperatures. The x-raydiffraction studies showed the four characteristic reflection values[(002), (100), (004), and (110)] for carbon nanotubes and the patternfor fcc-cobalt and cobalt oxide nanoparticles. The x-ray (002)reflection for carbon nanotubes was readily apparent.

EXAMPLE 35

Direct formation of fibers from melt of 1/20 by weightCo₂(CO)₈/naphthalene-derived mesophase pitch (AR pitch resin byMitsubishi) mixture—A sample (0.2 g) of the mixture prepared in Example33 was melted at 290° C. under inert condition and a glass rod wasinserted and a fiber was pulled out. This procedure was repeated severaltimes. The fibers were air stabilized by heating under a flow of air at1° C./min to 290° C. and holding for 1 hr. After cooling, the stabilizedfibers were heated and carbonized at 5° C./min to 1500° C. and held atthis temperature for 1 hr; the fibers retained their shape. X-raydiffraction studies showed the four characteristic reflection values[(002), (100), (004), and (110)] for carbon nanotubes and the patternfor fcc-cobalt and cobalt oxide nanoparticles. The x-ray (002)reflection for carbon nanotubes is readily apparent. TEM studies alsoshowed the presence of carbon nanotubes. Thus, this experiment showedthat fibers can be spun from the melt of such a mixture as Example 33,air stabilized, and converted in situ into carbon nanotube containingfibers. The yields in such fibers would depend on the optimization ofthe carbonization/graphitization conditions.

EXAMPLE 36

Fabrication of CNT fibers from the Co₂(CO)₈/phthalonitrile/p-BAPSsample—A sample of the Co₂(CO)₈/phthalonitrile mixture from Example 19(250 mg) and p-BAPS (12.5 mg) were placed in an aluminum pan. Themixture was heated at 350° C. with stirring and held at that temperatureuntil the mixture became too viscous to stir easily. A glass rod wasinserted into the mixture and pulled out resulting in the formation offibers from the surface of the mixture and attached to the glass rod.The diameter of the fibers was controlled by the rate that the fiberswere drawn. The polymeric fibers were heat treated at 200° C. for 2 hr,250° C. for 12 hr in air and 300° C. for 4 hr, 350° C. for 2 hr and 375°C. for 4 hr under argon. Different fibers were then carbonized byheating under nitrogen to 1000° C. and to 1500° C. at 0.3° C./min andholding for 1 hour to produce CNT-containing fibers. Higher yield ofCNTs were obtained for the higher temperature treated fibers. It wasimportant that the fibers be initially heated at a temperature below thetemperature of the melt so as to convert to a solid thermoset beforeheat treatment to higher temperatures.

EXAMPLE 37

Fabrication of CNT fibers from the 1:20 by weight Co₂(CO)₈/PAN mixture—Asample of the mixture prepared as in Example 1 (200 mg) was dissolved inDMF (2 mL) by heating at 100° C. until a homogeneous solution wasobtained. The mixture was then drawn into a 1 mL syringe and slowlyprecipitated into water yielding PAN polymeric fibers. The fiber shapedstructures obtained were isolated and dried. The shaped solid fiberswere oxidatively stabilized by heating at 280° C. for 3 hr so that thefibers would retain their shape and not melt upon further heat treatmentat elevated temperatures. Different stabilized fibers were thencarbonized by heating under nitrogen to 1000° C. and to 1500° C.,respectively, at 0.3° C./min and holding for 1 hour to produceCNT-containing fibers. Higher yield of CNTs were obtained for the highertemperature treated fibers.

EXAMPLE 38

Fabrication of CNT fibers from the 1:20 by weight Fe₂(CO)₉/PAN sample—Asample of the Fe₂(CO)₉/PAN mixture prepared as in Example 13 (250 mg)was dissolved in DMF (2 mL) with heating (100° C.) until a homogeneoussolution was obtained. The mixture was drawn into a 1 mL syringe andslowly precipitated into water yielding fibers. The fiber shapedstructures obtained were isolated, washed several times with distilledwater, and dried. The shaped solid fibers were oxidatively stabilized byheating at 280° C. for 2-3 hr so that the fibers would retain theirshape and not melt upon further heat treatment at elevated temperatures.Different polymeric fibers were then carbonized by heating undernitrogen to 1000° C. and to 1500° C., respectively at 0.3° C./min, andholding for 1 hour to produce in situ CNT-containing fibers. Higheryield of CNTs were obtained for the higher temperature treated fibers.

EXAMPLE 39

Synthesis of 1/20 by weight Ni[COD]₂/PAN mixture—Ni[COD]₂(50 mg, 0.181mmol) dissolved in 1 mL of methylene chloride was added dropwise to amixture of PAN (1.00 g) and 30 mL of methylene chloride in a 50 mL roundbottomed flask. The PAN did not dissolve. The slurry was allowed to stirfor 15 min before the solvent was removed under reduced pressure. Themixture was vacuum dried and isolated as an off-white solid.

EXAMPLE 40

Thermal conversion of 1/20 by weight Ni[COD]₂/PAN mixture to carbonnanotube-nickel nanoparticle composition by heating to 1000° C.—A sampleof the mixture from Example 39 (25.23 mg) was heated in a TGA chamberunder nitrogen at 10° C./min to 1000° C. resulting in a shapedcomposition and a char yield of 36%. The DTA curve showed an exotherm at308° C. X-ray studies confirmed the presence of carbon nanotubes-cobaltnanoparticles in the carbon composition. The x-ray diffraction studiesshowed the four characteristic reflection values [(002), (100), (004),and (110)] for carbon nanotubes and the pattern for nickelnanoparticles. The x-ray (002) reflection for carbon nanotubes wasreadily apparent.

EXAMPLE 41

Large scale synthesis of 1/20 by weight Fe₂(CO)₉/PAN mixture—PAN (250 g)and 1500 mL of methylene chloride were added to a 3000 mL three-neckedflask with a mechanical stirrer. The mixture was degassed with nitrogenfor 30 min. Fe₂(CO)₉ (12.5 g) was then added which readily dissolved inthe methylene chloride forming an orange colored suspension since thePAN did not dissolve. The slurry was allowed to stir for 1 hr before thesolvent was removed under reduced pressure. The solid was vacuum dried.

EXAMPLE 42

Large scale synthesis of 1/20 by weight Co₂(CO)₈/PAN mixture—PAN (250 g)and 1500 mL of methylene chloride were added to a 3000 mL three-neckflask with a mechanical stirrer. The mixture was degassed with nitrogenfor 30 min. Co₂(CO)₈ (12.5 g) was then added which readily dissolved inthe methylene chloride forming a dark red colored suspension since thePAN did not dissolve. The slurry was allowed to stir for 1 hr before thesolvent was removed under reduced pressure. The solid was vacuum dried.

EXAMPLE 43

Conversion of 1/20 by weight Fe₂(CO)₉/PAN mixture to polymeric nanofibersheets—Samples of the mixture from Example 41 were dissolved in DMF at80° C. to a desired viscosity and used in electrospinning to obtainrandom and aligned polymeric (PAN) nanofiber-containing sheets. Variousthicknesses (50, 100, and 200 μm) of the sheets (9″×18″) were formulatedand used for further studies.

EXAMPLE 44

Oxidative stabilization of polymeric (PAN) nanofiber sheets formulatedfrom 1/20 by weight Fe₂(CO)₉/PAN mixture—The polymeric nanofiber sheetsof Example 43 were oxidatively stabilized by heating at 1.5° C./min to260° C. and holding at this temperature for 3-5 hr in a flow of airfollowed by rapid heating (5° C./min) to 300° C. followed by cooling.The color of the sheets changed from off white to a dark tan color.

EXAMPLE 45

Conversion of the oxidatively stabilized polymeric (PAN) nanofibersheets formulated from 1/20 by weight Fe₂(CO)₉/PAN mixture to carbonnanotube-containing nanofiber carbon sheets—The air stabilized polymericsheets of Example 44 were heated at 5° C./min to 1000° C. under a flowof nitrogen and held at 1000° C. for 2 hr. During the heat treatment,the polymeric sheet shrunk to about ⅓ of the original size. X-raydiffraction showed that carbon nanotubes were being formed in situwithin the nanofibers of the carbon sheets along with some amorphouscarbon and iron oxide nanoparticles.

EXAMPLE 46

Heat treatment of carbon nanotube-containing nanofiber carbon sheetsformulated from the oxidatively stabilized polymeric (PAN) nanofibersheets to 1500° C.—Samples of the carbon nanotube-nanofiber carbonsheets of Example 45 were further heated at 5° C./min to 1500° C. andheld at this temperature for 2 hr under a flow of nitrogen. X-raydiffraction studies showed a large 002 peak at about 25.83 and the peakattributed to the amorphous carbon had been greatly diminished. Thisstudy showed that the amount of carbon nanotubes within the nanofiberscan be controlled as a function of the heat treatment temperature.

EXAMPLE 47

Conversion of sample formulated from the large scale synthesis of 1/20by weight Co₂(CO)₈/PAN mixture into films—A sample (0.5 g) of themixture of Example 42 was dissolved in 25 mL of DMF at 80° C. Uponcooling to ambient conditions, aliquots were poured into distilled waterforming solid films. The off white colored films were washed severaltimes with distilled water, collected, and dried.

EXAMPLE 48

Oxidative stabilization of sample (film) formulated from 1/20 by weightCo₂(CO)₈/PAN mixture—A sample (10 mg) of the off white colored film fromExample 47 was heated in a flow of air at 2° C./min to 225° C. and heldat this temperature for 4 hr. The oxidatively heat treatment convertedthe PAN into an unsaturated conjugated black material; sample lost about5% weight during the heat treatment.

EXAMPLE 49

Conversion of oxidatively stabilized PAN film to Co metalnanoparticle-carbon nanotube containing film—A sample of the stabilizedfilm from Example 48 (45 mg) was heated in a TGA chamber under flow ofnitrogen at 10° C./min to 1300° C. resulting in a shaped composition anda char yield of 50%. At 1000, 1100, and 1300° C., the sample retainedabout 58, 53, and 59% weight. X-ray studies confirmed the presence ofcarbon nanotubes-cobalt nanoparticles in the carbon composition of thefilm. The x-ray diffraction studies showed the four characteristicreflection values [(002), (100), (004), and (110)] for carbon nanotubesand the pattern for fcc-cobalt nanoparticles. The x-ray (002) reflectionat about 25.65 for carbon nanotubes is intense and readily apparent.This composition may be suitable for the spinning of fibers, oxidativestabilization, and conversion to carbon and graphite fibers.

EXAMPLE 50

Conversion of 1/20 by weight Co₂(CO)₈/PAN mixture—Samples of a mixtureas formed in Example 42 are dissolved in DMF to a desired viscosity andused in electrospinning to obtain random and aligned polymeric (PAN)nanofiber-containing sheets. Various thickness (50, 100, and 200 μm) ofthe sheets (9″×18″) and nanofiber diameter sizes are formulated and usedfor further studies and conversion to carbon nanotubes in situ withinthe nanofibers of carbon sheets.

EXAMPLE 51

Oxidative stabilization of polymeric (PAN) nanofiber sheets formulatedfrom 1/20 by weight Co₂(CO)₈/PAN mixture—The polymeric nanofiber sheetsof Example 50 are oxidatively stabilized by heating at 1.5° C./min to230-260° C. and holding at the temperature for 3-5 hr in a flow of airfollowed by rapid heating (5° C./min) to 300° C. followed by cooling.The color of the sheets is expected to change from off white to a darkcolor.

EXAMPLE 52

Conversion of the oxidatively stabilized polymeric (PAN) nanofibersheets formulated from 1/20 by weight Co₂(CO)₈/PAN mixture to carbonnanotube-containing nanofiber carbon sheets—The air stabilized polymericsheets of Example 51 are heated at 5° C./min to 1000° C. under flow ofnitrogen and held at 1000-1200° C. for 2 hr. During the heat treatment,the polymeric sheet is expected to shrink in size. X-ray diffractionstudies are expected to show that Co nanoparticle-carbon nanotubes areformed in situ within the nanofibers of the carbon sheets along withsome amorphous carbon and Co oxide nanoparticles.

EXAMPLE 53

Heat treatment of carbon nanotube-containing nanofiber carbon sheetsformulated from the oxidatively stabilized polymeric (PAN) nanofibersheets to 1500° C.—Samples of the carbon nanotube-nanofiber carbonsheets of Example 52 are further heated at 5° C./min to 1500° C. andheld at this temperature for 2 hr under a flow of nitrogen. X-raydiffraction studies are expected to show a large 002 peak at about 25.83and the peak attributed to the amorphous carbon is expected to begreatly diminished. This study is expected to show that the amount ofcarbon nanotubes within the nanofibers can be controlled as a functionof the heat treatment temperature.

EXAMPLE 54

Formulation of wt. % solutions in DMAC from 1/20 by weight Fe₂(CO)₉/PANmixture—Varying wt. % polymeric solutions in DMAC were prepared usingthe Fe₂(CO)₉/PAN mixture of Example 41 and thoroughly mixed by heatingat 120° C. for 1 hr. It was found that an 18 wt. % solution had the mostdesirable viscosity value for spinning fibers.

EXAMPLE 55

Spinning of fibers from 1/20 by weight Fe₂(CO)₉/PAN insolution—Polymeric fibers (100 filament tow) were spun using a spinneretfrom the mixture of Example 54, passed into water, and dried. The colorof the fibers/tows was a bit yellow-brown compared to homopolymer PAN,which was white. But this was expected as the Fe₂(CO)₉/PAN powder had adarker color relative to pure PAN attributed to the presence of theFe₂(CO)₉.

EXAMPLE 56

Oxidative stabilization of the fibers spun from a solution of 1/20 byweight Fe₂(CO)₉/PAN mixture—To oxidatively stabilize the PAN-basedfibers formulated in Example 55, the fibers/tows were heated from roomtemperature to 250° C. at 1° C./min in a flow of air; dwell time at 250°C. was for 5 hr followed by heating at 1° C./min to 300° C. and thencooling back to room temperature. During the heat treatment, the fiberschanged in color from light yellow-brown to amber to dark brown toblack.

EXAMPLE 57

Carbonization of the oxidatively stabilized Fe-Pan fibers at 1300°C.—Oxidatively stabilized fibers of Example 56 were mounted onto agraphite rack system and carbonized in a graphitic furnace in inert gas(helium). The stabilized fibers were heated under a constant tensionfrom room temperature to 1300° C. at 10° C./min and allowed to dwell at1300° C. for 1 hr followed by cooling back to room temperature at 50°C./min. The fibers had weight retention of 49.39%. Scanning electronmicroscopy studies of the black fibers showed the presence of carbonnanotubes within the fibers that had been formed in situ within thefibers during the carbonization process; the carbon nanotubes weremostly aligned along the direction of the fibers. Transmission electronmicroscopy studies showed the presence of carbon nanotubes and Fenanoparticles within the fibers.

EXAMPLE 58

Graphitization of the oxidatively stabilized Fe-Pan fibers at 2700°C.—Oxidatively stabilized fibers of Example 56 were mounted onto agraphite rack system and graphitized in a graphitic furnace in inert gas(helium). The stabilized fibers were heated under a constant tensionfrom room temperature to 1300° C. at 10° C./min and allowed to dwell at1300° C. for 1 hr followed by heating at 50° C./min to 2700° C. anddwelling at 2700° C. for 1 hr and cooling back to room temperature at50° C./min. The fibers had weight retention of 47.77%. Scanning electronmicroscopy studies of the black fibers showed the presence of carbonnanotube within the fibers that had been formed in situ within thefibers during the carbonization and graphitization processes; the carbonnanotubes were mostly aligned along the direction of the fibers.Transmission electron microscopy studies showed the presence of carbonnanotubes within the fibers.

EXAMPLE 59

Formulation of wt. % solutions in DMAC from 1/20 by weight Co₂(CO)₈/PANmixture—Varying wt. % polymeric solutions in DMAC were prepared usingthe Co₂(CO)₈/PAN mixture of Example 42 and thoroughly mixed by heatingat 120° C. for 1 hr.

EXAMPLE 60

Spinning of fibers from 1/20 by weight Co₂(CO)₈/PAN mixture—Polymericfibers (100 filament tow) are spun using a spinneret from the mixture ofExample 59, passed into water, and dried. The color of the fibers/towsis expected to be white based on the formation of films of Example 47from the deposition of the solution in water and drying of the filmsresulting in white film. The white fibers/tows are stabilized in air toconvert the polymer into a conjugated system that is expected to retainits structural integrity during carbonization and graphitization.

EXAMPLE 61

Oxidative stabilization of the fibers spun from a solution of 1/20 byweight Co₂(CO)₈/PAN mixture—To oxidatively stabilize the PAN-basedfibers/tows formulated in Example 60, the fibers/tows are heated fromroom temperature to 250° C. at 1° C./min in a flow of air; dwell time at250° C. is for 5 hr followed by heating at 1° C./min to 300° C. and thencooling back to room temperature. During the heat treatment, thefibers/tows are expected to change in color from off-white to amber todark brown to black.

EXAMPLE 62

Carbonization of the oxidatively stabilized Co-Pan fibers at 1300°C.—Oxidatively stabilized fibers/tows of Example 61 are mounted onto agraphite rack system and carbonized in a graphitic furnace in inert gas(helium). The stabilized fibers/tows are heated under a constant tensionfrom room temperature to 1300° C. at 10° C./min and allowed to dwell at1300° C. for 1 hr followed by cooling back to room temperature at 50°C./min. Scanning electron microscopy studies of the black fibers areexpected to show the presence of carbon nanotube within the fibersformed in situ within the fibers during the carbonization process withthe carbon nanotubes mostly aligned along the direction of the fibersbased on the results of Example 49. Transmission electron microscopystudies should show the presence of carbon nanotubes and Conanoparticles within the fibers as in Example 57.

EXAMPLE 63

Graphitization of the oxidatively stabilized Co-Pan fibers at 2700°C.—Oxidatively stabilized fibers of Example 61 are mounted onto agraphite rack system and graphitized in a graphitic furnace in inert gas(helium). The stabilized fibers are heated under a constant tension fromroom temperature to 1300° C. at 10° C./min and allowed to dwell at 1300°C. for 1 hr followed by heating at 50° C./min to 2700° C. and dwellingat 2700° C. for 1 hr and cooling back to room temperature at 50° C./min.Scanning electron microscopy studies of the black fibers should show thepresence of carbon nanotube within the fibers formed in situ within thefibers during the carbonization and graphitization processes with thecarbon nanotubes aligned along the direction of the fibers. Transmissionelectron microscopy studies are expected to show the presence of carbonnanotubes within the fibers as in Example 58.

EXAMPLE 64

Synthesis of metal salt/naphthalene-derived mesophase pitch (AR pitchresin by Mitsubishi) mixture—Various concentrations of metal saltsand/or organometallic compounds/resins such as octacarbonyldicobalt,diironnonacarbonyl, and ferrocene-based materials are mixed with ARpitch resin. The metal salt-AR pitch resin composition are thoroughlymixed in powdered form and heated at an elevated temperature above wherethe AR pitch resin flows with stirring by mechanical means under inertcondition to homogeneously mix. These samples are then cooled to roomtemperature.

EXAMPLE 65

Spinning of fibers from 1/20 by weight Co₂(CO)₈/AR pitch resin mixture—Asample of 1/20 by weight Co₂(CO)₈/AR pitch resin mixture of Examples 33and 64 is used to spin fiber at 300-370° C. through a spinneret. Thefibers/filament passes through a nitrogen atmosphere as they leave thespinneret and before being taken up by a reel.

EXAMPLE 66

Stabilization of the mesophase AR pitch fibers produced from 1/20 byweight Co₂(CO)₈/AR pitch resin mixture—AR pitch fibers produced byExample 65 are stabilized to a thermoset by heating between 250-350° C.in an air atmosphere for 5-60 min. The fibers are oxidatively heated sothat they will not soften when heated to carbonization and the fibersshould be totally infusible so they will not sag during carbonization.

EXAMPLE 67

Carbonization of the mesophase AR pitch fibers derived from Co₂(CO)₈/ARpitch resin mixture—AR pitch thermosetting fibers produced by Example 66are carbonized by heating up to 2000° C. in an inert (helium) atmosphereand holding from 5-30 min. Carbon nanotubes are expected to grow in situwithin the fibers along with other carbonaceous materials. As carbonnanotubes were observed in Examples 34 and 35 on solid sample and fiberspulled from the melt and carbonized under similar conditions, fibersformed by this procedure using a spinneret (Example 65) should containcarbon nanotubes with the yield dependent on the carbonizationtemperature. X-ray diffraction, scanning electron microscopy, andtransmission electron microscopy studies are used to analyze the fibersfor the carbon nanotubes.

EXAMPLE 68

Spinning of fibers from 1/20 by weight Fe₂(CO)₉/AR pitch resin mixture—Asample of 1/20 by weight Fe₂(CO)₉/AR pitch resin mixture of Example 64is used to spin fibers at 300-370° C. through a spinneret. Thefibers/filaments pass through a nitrogen atmosphere as they leave thespinneret and before being taken up by a reel.

EXAMPLE 69

Stabilization of the mesophase AR pitch fibers produced from 1/20 byweight Fe₂(CO)₉/AR pitch resin mixture—AR pitch fibers produced byExample 68 are stabilized to a thermoset by heating between 250-350° C.in an air atmosphere for 5-60 min. The fibers are oxidatively heated sothat they will not soften when heated to carbonization and the fibersshould be totally infusible so they will not sag during carbonization.

EXAMPLE 70

Carbonization of the mesophase AR pitch fibers derived from Fe₂(CO)₉/ARpitch resin mixture—AR pitch thermosetting fibers produced by Example 69are carbonized by heating up to 2000° C. in an inert (helium) atmosphereand holding from 5-30 min. Carbon nanotubes are expected to grow in situwithin the fibers along with other carbonaceous materials. As carbonnanotubes were observed in Examples 34 and 35 on solid sample and fiberspulled from melt and carbonized under similar conditions, small diameterfiber formed by this procedure should also have carbon nanotubes withthe yield dependent on the carbonization temperature. X-ray diffraction,scanning electron microscopy, and transmission electron microscopystudies are used to analyze the fibers for the carbon nanotubes.

EXAMPLE 71

Synthesis of 1/20 by weight octacarbonyldicobalt/polyacrylonitrile DMACmixture—Polyacrylonitrile (2.68 g) was dissolved over 2 h in 20 mL ofheated dimethylacetamide (DMAC). The mixture was cooled to ambienttemperature and Co₂(CO)₈ (134 mg, 0.332 mmol) was added. Gentle heatingto around 50° C. with stirring dissolved the Co₂(CO)₈ resulting in areddish-brown solution The mixture was used as prepared.

EXAMPLE 72

Thermal conversion of 1/20 by weightoctacarbonyldicobalt/polyacrylonitrile mixture to carbon nanotube-cobaltnanoparticle composition to 1000° C.—A sample of the mixture fromExample 70 was added to distilled water resulting in the deposition ofan oft-white solid. The solid was washed several times to remove thesolvent and then dried. A sample (50 mg) of the dried sample was heatedin a TGA chamber under nitrogen at 10° C./min to 1000° C. resulting in ashaped composition and a char yield of 50%. The DTA curve showed anexotherm at 308° C. X-ray studies confirmed the presence of carbonnanotubes-cobalt nanoparticles in the carbon composition. The x-raydiffraction study showed the four characteristic reflections [(002),(100), (004), and (110)] values for carbon nanotubes and the pattern forcobalt nanoparticles. The x-ray (002) reflection for carbon nanotubes isreadily apparent.

EXAMPLE 73

Fabrication of CNT fibers from the 1:20 by weightoctacarbonyldicobalt/polyacrylonitrile DMAC mixture—The solution fromExample 70 (200 mg) was drawn into a 1 mL syringe and slowlyprecipitated into water. Fiber shaped structures were obtained. Thefibers were washed several times with distilled water to remove thesolvent and then dried. The shaped solid fibers were oxidativelystabilized by heating in air at 280° C. for 2 h. The fibers were thencarbonized by heating under argon to 1000° C. at 0.3° C./min.

EXAMPLE 74

Synthesis of 1/20 by weight diironnonacarbonyl/polyacrylonitrile DMACmixture—Polyacrylonitrile (2.68 g) was dissolved over 2 h in 20 mL ofheated dimethylacetamide (DMAC). The mixture was cooled to ambienttemperature and Fe₂(CO)₉ (134 mg, 0.368 mmol) was added. Gentle heatingto around 50° C. with stirring dissolved the Fe₂(CO)₉ resulting in anorange-red solution. The mixture was used as prepared.

EXAMPLE 75

Thermal conversion of 1/20 by weight diironnonacarbonyl/polyacrylonitrile mixture to carbon nanotube-iron nanoparticlecomposition—A sample of the mixture from Example 73 was added todistilled water resulting in the deposition of an oft-white solid. Thesolid was washed several times to remove the solvent and then dried. Asample (43.5 mg) of the dried sample was heated in a TGA chamber undernitrogen at 10° C./min to 1000° C. resulting in a shaped composition anda char yield of 48%. The DTA curve showed an exotherm at 310° C. X-raystudies confirmed the presence of carbon nanotubes-iron nanoparticles inthe carbon composition. The x-ray diffraction study showed the fourcharacteristic reflections [(002), (100), (004), and (110)] values forcarbon nanotubes and the pattern for iron nanoparticles. The x-ray (002)reflection for carbon nanotubes is readily apparent.

EXAMPLE 76

Fabrication of CNT fibers from the 1:20 by weightdiironnonacarbonyl/polyacrylonitrile DMAC mixture—The solution fromExample 73 (500 mg) was drawn into a 1 mL syringe and slowlyprecipitated into water. Fiber shaped structures were obtained. Thefibers were washed several times with distilled water to remove thesolvent and then dried. The shaped solid fibers were oxidativelystabilized by heating in air at 280° C. for 2 h. The fibers were thencarbonized by heating under argon to 1000° C. at 0.3° C./min.

Obviously, many modifications and variations are possible in light ofthe above teachings. It is therefore to be understood that the claimedsubject matter may be practiced otherwise than as specificallydescribed. Any reference to claim elements in the singular, e.g., usingthe articles “a,” “an,” “the,” or “said” is not construed as limitingthe element to the singular.

What is claimed is:
 1. A nanofiber sheet comprising at least 15 wt. %carbon nanotubes.
 2. The nanofiber sheet of claim 1, wherein nanofibersheet further comprises metal nanoparticles.
 3. A nanofiber sheetcomprising a mixture of: a polymer or a resin; and a transition metalcompound; wherein the polymer or resin is an aromatic polymer or aprecursor thereof.
 4. The nanofiber sheet of claim 3, wherein thepolymer or resin is a phthalonitrile polymer, polyacrylonitrile, coalpitches, petroleum pitches, or pitch resins.
 5. The nanofiber sheet ofclaim 3, wherein the transition metal compound is octacarbonyldicobalt,1-(ferrocenylethynyl)-3-(phenylethynyl)benzene, diironnonacarbonyl, orbis(1,5-cyclooctodiene)nickel(0).
 6. A nanofiber sheet comprising: anaromatic polymer; and metal nanoparticles.
 7. The nanofiber sheet ofclaim 6, wherein the aromatic polymer is a phthalonitrile polymer or athermo-oxidative stabilized polyacrylonitrile, coal pitches, petroleumpitches, or pitch resins.